Geometric and hydrodynamic influences on the droplet breakup dynamics in a branched microdevice

Abstract

Droplet breakup phenomenon in a microchannel is a well-known potential approach for process intensification. Here we investigate a branched microdevice to explore the influence of Capillary number (Ca) and the ratio of branching arm width to the main channel (β) on droplet breakup dynamics by developing a 3-D computational model, which was firstly validated with the in-house as well as independent experimental results. A homogeneous pressure field inside a droplet is found to be the principal reason in droplet non-breakup for widely asymmetric configuration (i.e., β = 0.4 and 1.2). For other branching configurations (β = 0.6, 0.8 and 1.0), droplet breakup in three different regimes is identified, and a regime map is formulated as a function of Ca vs. β. It is observed that apart from Ca, a critical β also exists for the transition between breakup and non-breakup regimes, and the configuration with β = 0.8 is more susceptible for droplet breakup owing to the force balance in both arms with respect to confinement and flow direction. Additionally, the smaller critical Ca for β = 1.0 than for β = 0.6 indicates the significance of upstream flow distribution.